CO, HC, NOX, and so on to be harmful to human body are contained to exhaust gas being exhausted from a vehicle engine, and an apparatus for oxidizing or reducing the harmful exhaust gas to CO2, H2O, N2, and so on to be harmless is a catalytic converter.
As a catalytic converter applying an exhaust system of a vehicle, an exhaust manifold catalytic converter (MCC) and an underflow catalytic converter (UCC), which are mounted to a downstream end portion of an exhaust manifold, have been used. Particularly, the MCC catalyst is mounted at a downstream end portion of the exhaust manifold in which a temperature of exhaust gas is relatively high, in order to revitalize a catalyst as fast as possible on starting and cooling of an engine.
A warm-up catalytic converter (WCC) effectively oxidizing not only a CO element and a HC element but also a SOF element which are contained in exhaust gas is applied for responding to the exhaust gas regulation which is recently to be reinforced.
FIG. 1 is a schematic diagram of a structure of a warm-up catalytic, and FIG. 2 is a cross-sectional view of A of FIG. 1 according to a conventional art. Referring to FIG. 1 and FIG. 2, a shell extends toward a front cone such that the shell and the front cone are engaged by welding in a conventional art. At this time, a stainless steel (SUS) cast steel is mostly used as a material of the front cone, and a general SUS material (particularly, SUS4 stainless steel) is mostly used as a material of the shell.
The above mentioned conventional art can be stably used on the ordinary engine output, but there is a problem that a crack is generated at a rear end of a shell welding portion by thermal fatigue accumulation and thermal stress focus in a high power engine which is recently applied. Particularly, a structure of a warm-up catalytic converter (WCC) may have been altered to be bent because an interior space of an engine compartment is small when a high power engine is mounted to a small vehicle, and in this case, there is a problem that durability is frequently deteriorated as thermal fatigue accumulation and thermal stress focus rapidly occur.
The foregoing is intended merely to aid in the understanding of the background of the present disclosure, and is not intended to mean that the present disclosure falls within the purview of the related art that is already known to those skilled in the art.